Method of making a filamentary laminate and the products thereof

ABSTRACT

The present invention is directed to a nonwoven composite fabric comprising one or more layers of discontinuous filaments or nano-fiber filaments positioned between at least one continuous filament web and one cellulosic fiber web that are subsequently hydroentangled, wherein the discontinuous filaments or nano-fiber filaments provide a barrier to prevent the loss of the cellulosic fibrous material through the highly porous continuous filament web.

TECHNICAL FIELD

The present invention relates generally to hydroentangled (spunlaced)nonwoven fabrics, and more particularly to hydroentangled laminatenonwoven laminate comprising one or more continuous filament webs, finedenier filament webs, and a cellulosic fiber web, which are integratedso that the cellulosic fibers become integrated with the filamentarystructure. Nonwoven fabrics embodying the present invention exhibitunique performance attributes, such as improved barrier characteristics,excellent strength and absorbency, and is particularly suited for use inhygiene, medical, and industrial applications

BACKGROUND OF THE INVENTION

Nonwoven fabrics are used in a wide variety of applications where theengineered qualities of the fabrics can be advantageously employed. Theuse of selected thermoplastic polymers in the construction of thefibrous fabric component, selected treatment of the fibrous component(either while in fibrous form or while in an integrated structure), andselected use of various mechanisms by which the fibrous component isintegrated into a useful fabric, are typical variables by which toadjust and alter the performance of the resultant nonwoven fabric.

Formation of nonwoven fabrics by hydroentanglement (spunlacing) isparticularly advantageous in that the fibers or filaments from which thefabric is formed can be efficiently integrated and oriented as may bedesired for a specific application. Blends of different types of fiberscan be readily combined by hydroentanglement so that resultant fabricsexhibiting selected physical properties can be fabricated.

Continuous filament fabrics are relatively known for being highlyporous, and ordinarily require an additional component in order toimpart a barrier performance. Typically, barrier performance has beenenhanced by the use of a barrier “melt-blown” layer of very finefilaments, which are drawn and fragmented by a high velocity air stream,and deposited into a self-annealing mass. Typically, such a melt-blownlayer exhibits very low porosity, enhancing the barrier properties oflaminate fabrics formed with spunbond and melt-blown layers.

Heretofore, nonwoven fabrics formed from blends of continuous filamentsand cellulosic fibers have been known, with such fabrics desirablyexhibiting physical properties which are characteristic of theconstituent synthetic and cellulosic fibers. Typically, synthetic fiberscan be formed into a fabric so that the characteristics such as goodabrasion resistance and tensile strength can be provided in theresultant fabric. The use of cellulosic fibers provides such fabricswith desired absorbency and softness.

U.S. Pat. No. 5,459,912, to Oathout, hereby incorporated by reference,discloses patterned, spunlaced fabrics formed from synthetic fibers andwood pulp which are stated as exhibiting good absorbency, and lowparticle counts. The fabrics are thus suited for use where thesecharacteristics are desirable, such as for use as wipes in clean rooms,wipes for food service, and like applications. However, this patentcontemplates integration of wood pulp fibers and synthetic fibers in adry state, with subsequent hydroentanglement by treatment on one sideonly (prior to aperturing). It is believed that this results insignificant loss of the wood pulp fibrous material through the looselybonded synthetic fibers, thus detracting from the efficiency of themanufacturing process.

Additionally, the juxtaposition of continuous filament webs and pulpfibers, with subsequent hydroentanglement has shown significant loss ofthe wood pulp fibrous material through the filaments due to high levelof porosity within the continuous filament web. Because laminatenonwoven fabric materials formed from continuous filament and cellulosicfibers can provide a combination of desirable physical properties, thepresent invention is directed to a method of making such a laminatenonwoven fabric which facilitates efficient fabric formation by abatingloss of cellulosic fibers to the filtrate water during integration byhydroentanglement.

SUMMARY OF THE INVENTION

The present invention is directed to a nonwoven composite fabriccomprising one or more layers of discontinuous filaments or nano-fiberfilaments positioned between at least one continuous filament web andone cellulosic fiber web that are subsequently hydroentangled, whereinthe discontinuous filaments or nano-fiber filaments provide a barrier toprevent the loss of the cellulosic fibrous material through the highlyporous continuous filament web.

In accordance with the present invention, the discontinuous filament ornano-fiber layer is lightweight, less than 2 grams per square meter. Thediscontinuous filaments or nano-fiber filaments may be directly extrudedonto the continuous filament web or alternately, unwound and positionedatop the continuous filament web.

The thermoplastic polymers of the continuous filament and discontinuousfilament layer or layers are chosen from the group consisting ofpolyolefins, polyamides, and polyesters, wherein the polyolefins arechosen from the group consisting of polypropylene, polyethylene, andcombinations thereof. It is within the purview of the present inventionthat the continuous filament spunbond layer or layers may compriseeither the same or different thermoplastic polymers. Further, thecontinuous filaments of the spunbond layer or layers may comprisehomogeneous, bi-component, and/or multi-component profiles and theblends thereof.

Once the discontinuous filament or nano-fiber layer is positioned atopthe continuous filament web, the cellulosic fibrous material of thepresent fabric is introduced by juxtaposing the cellulosic fibrous webatop the discontinuous filament layer or nano-fiber layer. The layeredwebs are then hydroentangled, and subsequently dried to form the presentcomposite nonwoven fabric. Notably, the incorporation of a discontinuousfilament or nano-fiber layer has been found to desirably minimize lossof the cellulosic material as the various layers are integrated byhydroentanglement.

Other features and advantages of the present invention will becomereadily apparent from the following detailed description, theaccompanying drawing, and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic illustration of a process embodying theprinciples of the present invention.

DETAILED DESCRIPTION

While the present invention is susceptible of embodiment in variousforms, there will hereinafter be described, presently preferredembodiments, with the understanding that the present disclosure is to beconsidered as an exemplification of the invention, and is not intendedto limit the invention to the specific embodiments disclosed herein.

he present invention is directed to a nonwoven composite fabriccomprising a combination of desirable physical properties. Thehydroentangled continuous filament layer, discontinuous filament ornano-fiber layer, and cellulosic layer provide a soft and absorbentfabric suitable for various hygiene, medical, and industrial end-useapplications, such as wipes and protective cover materials. It has beencontemplated that the addition of a discontinuous filament or nano-fiberlayer positioned between a continuous filament layer, or spunbond layer,and pulp layer, optimizes the measure of cellulosic fiber within theproduct due to the inability of the fiber to be washed away in thehydroentanglement process.

A process for the formation of spunbond involves supplying a moltenpolymer, which is then extruded under pressure through a large number oforifices in a plate known as a spinneret or die. The resultingcontinuous filaments are quenched and drawn by any of a number ofmethods, such as slot draw systems, attenuator guns, or Godet rolls. Thecontinuous filaments are collected as a loose web upon a movingforaminous surface, such as a wire mesh conveyor belt. When more thanone spinneret is used in line for the purpose of forming a multi-layeredfabric, the subsequent webs is collected upon the uppermost surface ofthe previously formed web. The web is then at least temporarilyconsolidated, usually by means involving heat and pressure, such as bythermal point bonding. Using this bonding means, the web or layers ofwebs are passed between two hot metal rolls, one of which has anembossed pattern to impart and achieve the desired degree of pointbonding, usually on the order of 10 to 40 percent of the overall surfacearea being so bonded.

A process related to the formation of spunbond is the meltblown process,which involves the formation of discontinuous filaments. Again, a moltenpolymer is extruded under pressure through orifices in a spinneret ordie. High velocity air impinges upon and entrains the filaments as theyexit the die. The energy of this step is such that the formed filamentsare greatly reduced in diameter and are fractured so that microfibers offinite length are produced. This differs from the spunbond processwhereby the continuity of the filaments is preserved. The process toform either a single layer or a multiple-layer fabric is continuous,that is, the process steps are uninterrupted from extrusion of thefilaments to form the first layer until the bonded web is wound into aroll. Methods for producing these types of fabrics are described in U.S.Pat. No. 4,041,203. The meltblown process, as well as thecross-sectional profile of the spunbond filament or meltblownmicrofiber, is not a critical limitation to the practice of the presentinvention.

A nano-fiber of finite or infinite length may also be utilized in thepresent invention, wherein the average fiber diameter of the nano-fiberis in the range of less than or equal to 1000 nanometers, and preferablyless than or equal to 500 nanometers. Formation of fabrics fromnano-fibers, particularly when a light basis weight nano-fiber barrierlayer is preferred, is either coated or “dusted” onto a substrate layer.The present invention may utilize a nano-fiber layer of less than about2 grams per square meter.

In accordance with the present invention and as noted in FIG. 1, ameltblown layer or nano-fiber layer 4 is directly extruded onto, orunwound and positioned adjacent a spunbond layer 2. Subsequently, acellulosic fiber web 6 is juxtaposed with the meltblown layer ornano-fiber layer 4 for formation of the present composite nonwovenfabric. The cellulosic fibers are provided in the form of wood pulpfibers introduced in the form of a wetlaid web, commonly referred to as“tissue”.

At this stage in the process, the juxtaposed layers are subjected tohydroentanglement under the influence of high pressure liquid streamsgenerated by suitable manifolds 14 positioned above an entangling belt12. As illustrated in FIG. 1, the high pressure liquid streams from themanifolds 14 are directed against a first expansive surface of thejuxtaposed webs. Thereafter, the layers are directed about anotherentangling device, such as drum 18, with high pressure liquid streamsfrom manifolds 22 directed against the opposite expansive surface of thewebs. The now integrated webs can be transferred over a dewatering slot,then dried at 24 and wound for storage and shipment.

Optionally, the entangled nonwoven composite may include additionalfabric layers, as well as film layers. Such film layers may include oneor more breathable, apertured, imaged films. Further, the compositefabric may be imparted with a three-dimensional image. The entanglingapparatus may further include an imaging foraminous surface, such as athree-dimensional imaging drum comprising a three-dimensional imagetransfer device for effecting imaging of the now-entangled laminate.Such three-dimensional image transfer devices are disclosed in U.S. Pat.No. 5,098,764, which is hereby incorporated by reference. The imagetransfer device includes a moveable imaging surface which moves relativeto a plurality of entangling manifolds which act in cooperation withthree-dimensional elements defined by the imaging surface of the imagetransfer device to affect additional imaging and patterning of thefabric being formed.

As will be appreciated, a fabric formed in accordance with the presentinvention need not be subjected to hydroentangling treatment bydirection of hydraulic water jets against both expansive surfaces of thefabric as it is formed. Additionally, it will be recognized that theillustrated nip rolls can be utilized to improve fabric density, andreduce the moisture content of the web prior to drying.

The composite nonwoven fabric of the present invention may be treatedwith one or more mechanical or chemical post treatments. For instance,the resultant fabric may be mechanically compacted and/or additivesimparted to achieve a specific performance within the fabric. Suchadditives may include pigments, thermochromics, fragrances, emollients,natural herbs and botanicals, UV chemistries, antimicrobials, and thecombinations thereof, as well as various other performance oraesthetically modifying additives. The composite of the presentinvention is suitable for various hygiene, medical, and industrialend-uses, whereby the composite is especially suitable for wipes.Incorporation of a discontinuous filament or nano-fiber layer positionedbetween a continuous filament layer, or spunbond layer, and pulp layer,optimizes the measure of cellulosic fiber within the product due to theinability of the cellulosic fiber to be washed away in thehydroentanglement process. As a result, the wipe product exhibitsimproved absorbency when utilized in a dry state and retains aqueousadditives better when utilized in a wet state.

From the foregoing, numerous modifications and variations can beeffected without departing from the true spirit and scope of the novelconcept of the present invention. It is to be understood that nolimitation with respect to the specific embodiment disclosed herein isintended or should be inferred. The disclosure is intended to cover, bythe appended claims, all such modifications as fall within the scope ofthe claims.

1. A method of making a composite nonwoven fabric, comprising the stepsof: providing a continuous filament web; providing a discontinuousfilament web, wherein said web has a basis weight less than about 2grams per square meter; providing a cellulosic fiber web;hydroentangling said webs to form a partially entangled web;hydroentangling said juxtaposed partially entangled web and cellulosicfiber web; and drying said hydroentangled webs to form said nonwovenfabric.
 2. A method of making a laminate nonwoven fabric in accordancewith claim 1, wherein said continuous filament web may be selected fromthe group consisting of polyolefins, polyamides, polyesters, and theblends thereof.
 3. A method of making a laminate nonwoven fabric inaccordance with claim 2, wherein said polyolefins may be selected fromthe group consisting of polypropylene, polyethylene, and combinationsthereof.
 4. A method of making a laminate nonwoven fabric in accordancewith claim 1, wherein said step of hydroentangling said juxtaposed webscomprises first directing high-pressure liquid streams against a firstexpansive surface of said juxtaposed webs, and thereafter directinghigh-pressure liquid streams against an opposite expansive surface ofsaid juxtaposed web.
 5. A method of making a laminate nonwoven fabric inaccordance with claim 1, wherein said laminate comprises additional woodpulp layers, continuous or discontinuous filaments layers, film layers,or a combination thereof.
 6. A method of making a laminate nonwovenfabric, comprising the steps of: providing a continuous filament web;providing a foraminous surface; hydroentangling said continuous filamentweb to form a partially entangled web; juxtaposing a cellulosic fiberweb with said partially entangled web; advancing said juxtaposedpartially entangled web and cellulosic fiber web onto said foraminoussurface and hydroentangling said webs on said surface so as to impart atleast one three-dimensional image into said laminate; and drying saidhydroentangled webs to form said nonwoven fabric.
 6. A method of makinga laminate nonwoven fabric in accordance with claim 6, wherein saidforaminous surface is a three-dimensional image transfer device.
 7. Amethod of making a laminate nonwoven fabric in accordance with claim 6,wherein: said step of hydroentangling said juxtaposed partiallyentangled web and paper web comprises first directing high-pressureliquid streams against a first expansive surface of the juxtaposed webs,and thereafter directing high-pressure liquid streams against anopposite expansive surface of said juxtaposed web.
 8. A method of makinga laminate nonwoven fabric as in claim 1, wherein said laminate is awipe.
 9. A method of making a laminate nonwoven fabric as in claim 6,wherein said laminate is a wipe.
 10. A method of making a compositenonwoven fabric, comprising the steps of: providing a continuousfilament web; providing a discontinuous filament web, wherein said webhas a basis weight less than about 2 grams per square meter; providing acellulosic fiber web; juxtaposing said webs; hydroentangling said webs;and drying said hydroentangled webs to form said nonwoven fabric.
 11. Amethod of making a laminate nonwoven fabric in accordance with claim 10,wherein said step of hydroentangling said juxtaposed webs comprisesfirst directing high-pressure liquid streams against a first expansivesurface of said juxtaposed webs, and thereafter directing high-pressureliquid streams against an opposite expansive surface of said juxtaposedweb.